The amplitude of a damped oscillator decreases to 0.9 times its original magnitude is 5 s. In another 10 s it will decrease to `alpha` times its original magnitude, where `alpha` equals :

Options

A. 0.81
B. 0.729
C. 0.6
D. 0.7

Answer

B

Explanation

For damped oscillator amplitude at any time is
`A=A_(0)e^(-kt)`
`implies" "0.9A_(0)=A_(0)e^(-5k)`
and `" "A_(0)=A_(0)e^(-15k)`
solving `impliesalpha=0.739`
So, correct choice is (b).